One of the charges often made by climate change sceptics about climate change believers is that they sometimes manipulate statistics. The believers say exactly the same thing about the sceptics.
What are we to make of such allegations? By 'we' I mean the vast majority of humanity who are not experts on climate change. These include most politicians and journalists, all non-scientists, and even scientists in unrelated fields.
My own response is to assume both sides are capable of twisting the facts. This is not based on scientific knowledge of climate change, since like almost everyone else I don't have any.
You could say it is a common sense point of view. In any heated argument, both sides are liable to be selective, and we shouldn't expect scientists to be immune from such tendencies.
It is nonetheless shocking to read leaked emails from the University of East Anglia which imply selectivity.
The university may not be generally regarded as one of this country's finest academic institutions, but its Climatic Research Unit (CRU) is reckoned one of the most influential in the world.
In one email, dated November 1999, Professor Phil Jones, head of the CRU, wrote: 'I've just completed Mike's Nature [the scientific journal] trick of adding in the real temps to each series for the last 20 years (i.e. from 1981 onwards) and from 1961 to hide the decline.'
The CRU, which has played a key role in several United Nations reports, has refused to provide detailed information about the data underlying temperature records.
Other emails are no less damning. Some suggest efforts to prevent the publication of work by sceptics, or to keep it out of an Intergovernmental Panel On Climate Change.
In another email, Professor Jones refers to the death of a prominent sceptic by writing 'in an odd way this is cheering news'
These and other emails do not give a impression of relentless seeking after truth, or of constant fair-mindedness.
Rather, they hint at a tendency to conceal inconvenient facts in their own research and to suppress them in others.
What has been the response of the CRU in particular and climate change believers in general? With one or two honourable exceptions, such as George Monbiot in The Guardian newspaper, it has been unapologetic, and beside the point.
The University of East Anglia even refused to admit for a while that the emails were genuine.
There are those such as Professor Julia Slingo, chief scientist at the Met Office, who complain that the emails were obtained criminally, as though this somehow frees her and others from any responsibility to justify them.
There is also the hoary old defence that they have been taken out of context.
Defenders of the CRU have even argued that the emails span a period of some ten years, and are therefore bound to include a few disobliging references. Professor Jones has tried to explain away his email about tricks and hiding decline by saying it was written in haste.
This won't do. Even in haste, a prominent academic writing to a colleague does not say something he does not mean. Professor Jones should explain why he used words which would appear to be self-incriminating. I suspect he won't because he can't.
You may say that, just because a few leading climate change evangelists misbehave, it does not follow that all climate change believers do so, or that all their arguments are false.
That, of course, is true. But if there is evidence that one of the world's most influential climate change institutions has acted - to say the least - unprofessionally, it is not unreasonable to wonder whether such techniques are not more widely used.
Almost none of us will ever understand climate change. Without specialised scientific knowledge, most of us can only make an educated guess as to whether it is caused by man.
My guess is that it is to an extent. In coming to this tentative conclusion I am influenced by the integrity and sense of fair dealing of those who volubly make the argument for man-made climate change.
So when these people show a want of openness and fair dealing, and when they fail to offer a proper defence of apparently dodgy emails, such faith as I have in them is shaken. I may not understand climate change but I can recognise slippery responses when I see them.
But then this is not a debate that is often conducted in an open way. In some quarters climate change sceptics are derisively dismissed as 'deniers', which is to put them on the level of Holocaust deniers.
But whereas the Holocaust is a historical event, attested to by many survivors and observers, man-made climate change is only a theory, albeit a highly plausible one.
Its adherents invest it with the authority of an unchallengeable doctrine - which is why, when some of them are discovered not being wholly straightforward, they do not bother to offer a creditable defence.
And, even more disturbingly, much of the media does not feel obliged to put them on the spot, having uncritically swallowed everything they say.
Imagine that a leading climate change sceptic had been unmasked using this sort of language.
There would be a tremendous hullabaloo. BBC news bulletins, which have either ignored or underplayed the University of East Anglia's emails, would be full of fury.
The Corporation long ago stopped questioning the climate change consensus. Visit its website and you will find little, if anything, critical of the University of East Anglia.
But you can watch a video clip of Bianca Jagger, borrowed from its programme The Daily Politics, informing us that climate change is the biggest threat we face, with scenes of the Cumbrian floods in the background. She suggests they were caused by man-made climate change.
Bianca Jagger cannot possibly know whether or not they were, and nor does the BBC.
Her views about the causes of climate change are completely worthless, and yet the BBC cheerfully broadcasts them - as it would certainly not broadcast the views of an ignoramus who was a sceptic.
If climate change really is the biggest threat facing humanity, let's have a more measured and reasoned argument in which the sceptics are not shouted down or ignored.
If our way of life is to be changed, and our countryside transformed, and the Third World possibly deprived of the opportunities of economic growth, we deserve a bit more than bogus pictures of polar bears perched on lumps of ice, and Bianca Jagger informing us that the Cumbrian floods are the result of climate change.
And the University of East Anglia - a public institution largely funded by the taxpayer - owes the world a more straightforward explanation than it has so far bothered to give about those apparently discreditable emails.
The misbehaviour of one influential group in seeking to manipulate the facts obviously does not mean that all climate change believers are wrong.
But in future people would be wise no longer to take on trust their most outlandish and hair-raising claims.